This invention relates to a pure bacterial culture for degrading branched alkyl ethers, such as methyl t-butyl ether (MTBE), and branched alcohol such as t-butyl alcohol (TBA). The invention also relates to a process for preparing such culture.
Alkyl-alkyl ethers (Rxe2x80x94Oxe2x80x94R) such as methyl t-butyl ether (hereinafter xe2x80x9cMTBExe2x80x9d) are being used as octane-enhancers in the reformulation of low volatility unleaded gasoline blends and for reducing the emission of volatile organic compounds from engines. In general, alkylethers, especially those alkylethers which have only one ether linkage and without other functional groups, are chemically stable compounds and there is little information on their biodegradability in soil, groundwater and activated sludge environments. The very slow rate of alkylether degradation by indigenous microbes in soils and biosludges may be attributed to the very stable and chemically unreactive ether linkage, the inability of these compounds to be transported into cells and/or the lack of inducible or existing enzyme activities (e.g. oxygenases, hydroxylases) which can attack the ether bond.
It is known that MTBE can persist in groundwater from accidental spills of unleaded gasoline from underground storage tanks. Certain mixed bacterial culture(s) have been used to degrade MTBE. But, it is desirable to use a pure bacterial culture for degrading MTBE and TBA to effectively biotreat groundwater, wastewater, tank bottom wastes or soils containing these tertiary-carbon-containing ether and alcohols. This is because relatively large quantities of mixed culture are typically needed for degrading or remediating MTBE or TBA. However, only minor portions of mixed cultures contain microbes which are able to degrade MTBE or its metabolites. It is more costly to mass produce mixed cultures than pure cultures to obtain the same quantity of MTBE degradation activities.
U.S. Pat. No. 5,750,364, assigned to Shell Oil Company having J. P. Salanitro as the inventor, describes a mixed bacterial culture capable of degrading MTBE and TBA.
K. Mo, et al. Appl Microbiol Biotechnol (1997) 47:69-72 proposes isolating from activated sludge and fruit of the Gingko Tree three pure cultures, classified as belonging to the genuses Methylobacterium, Rhodococcus, and Arthrobacter, which are capable of degrading MTBE. However, the data presented by Mo proposes that only a minor portion of the MTBE was degraded by the cultures and very little if any, of MTBE degraded to carbon dioxide within the time frame of the experiment.
Thus, there remains a need for a pure bacterial culture capable of degrading an alkyl ether, especially a branched alkyl ether, specifically a tertiary carbon atom-containing ether such as MTBE, to carbon dioxide effectively within a short period of time under aerobic condition. There is also a need for the same for degrading branched alcohols, especially tertiary carbon atom-containing alcohols, such as t-butyl alcohol (TBA). The culture would be useful for treating wastes and groundwater contaminated with ethers, especially branched alkyl ethers such as MTBE, and branched alcohols such as TBA.
This invention relates to (a) a pure bacterial culture capable of degrading alkylethers, especially branched alkylethers including MTBE and branched alcohols such as t-butyl alcohol, under aerobic conditions; (b) a process for preparing such pure bacterial culture; (c) a process for the aerobic degradation of ethers, especially branched alkylethers such as MTBE, using a pure bacterial culture prepared from activated sludges; (d) a process for remediating wastewater and groundwater containing ethers, especially branched alkylethers such as MTBE, to reduce the alkylether(s) content thereof by growing in the presence of said wastewater and groundwater a population of a pure bacterial culture prepared from activated sludges; and (e) the use of said pure culture for degrading or remediating t-butyl alcohol containing aqueous solutions or groundwater.